Hastily written signs direct the way to the next cocktail - sorry, I mean press conference.

This is the 13th such summit to be held in Africa. The subject? A disease which is ravaging the continent. Here in Kenya, it's believed to kill one person a minute. A virus which has left 13 million orphans. Well, you've probably guessed it by now. I'm talking about HIV/Aids.

Some of you might be tempted at this point to go and make a cup of tea. Aids in Africa is a bit like drought or famine, or the poor.

Despite the efforts of global organisations, like the United Nations, these catastrophes - it sometimes seems - will always be with Africa.

Compassion fatigue

As the conference approached, we scratched our heads. What could we possibly do that was different?

We phoned programmes in London. We had a polite hearing, but the response came back: "Oh we've done Aids... George Bush was in Africa and talked about it, didn't he? And then there was a big conference in South Africa about it, wasn't there?"

Aids is exacting a grim toll on the younger generation

What more can we add? So what more CAN we add?

Well, let me tell you a story of two girls, Alice and Sarah. These are not their real names - I've changed them to protect their identities.

You won't find Alice and Sarah at cocktails or buffet dinners this week. But if you pick your way through the multiple policy statements, reports and speeches that emerge - blizzard-like - from these conferences, you will discover girls like Alice and Sarah at the quiet, silent centre of this storm.

What makes them so is their age, and gender. They are teenage girls - in the case of Alice, just blossoming into womanhood. Statistically, they are the group most vulnerable to HIV infection.

Alice is tall and thin - and looks a little older than her 13 years.

We talked at the home of a local charity worker, who specialises in vulnerable children. We sat around the table, cups of tea cooling in front of us, and Alice answered my questions.

I look at Alice - her face is swollen, there are dark bruises on her arms and legs. I ask her gently: "Alice, do you know your HIV status?" This child - turning into a woman - pauses and looks uncertain. There is a long silence. Finally, she says: "I worry that I am infected, because I know my stepbrother is sick."

Poverty

Let us go now across Nairobi to Mathare slum, one of the biggest in Africa.

Anti-Aids drugs are now cheaper - but still few Africans get them

In a dim shack, partitioned by a filthy blanket separating the bed from the sofa, sits Sarah. She lives with her mother, who struggles to get by with a small tailoring business.

But when Sarah became a teenager, she started to rail against the poverty of their circumstances. Like other adolescent girls, she wanted fashionable clothes to wear. A decent meal to eat.

She turned to casual prostitution - finding men who would pay for those things. Finally, one of them told her he was sick. She went for a test. She too is HIV positive.

I ask her: "What do you see the future as, Sarah?"

Again, there is a long silence. Tears well up and trickle down her pretty face. "I don't know... But I know I will not live long. My life will be short."

I have spoken to some middle-class mothers, who contemplate sending their daughters to Europe or America. In an Aids-ridden continent, the teenage years are simply too dangerous. They can be a death sentence.

But for impoverished girls like Sarah and Alice, there's no escape route. Indeed for Alice, shockingly, there seems little that can be done to save her from the nightly beatings and rapes.

As I leave, her neighbour and a child care worker discuss what can be done. But all the orphanages that might provide a refuge are full, and the legal process is cumbersome. As the discussion continues, Alice stands a little apart, listening, arms drawn close to her sides. She's shivering - even though it's hot in the midday sun.